The present invention relates to a nuclear fusion apparatus, and in particular, to the structure of a central support member for supporting a plurality of poloidal coils in a tokamak type nuclear fusion apparatus.
In a conventional tokamak type nuclear fusion apparatus such as the one disclosed in Japanese Laid-Open Pat. No. 54,3695, as shown in FIG. 1, a plurality of toroidal coils 2 are radially disposed around a central support stay 1, and a plurality of poloidal coils 3 are circumferentially disposed around the central support stay 1 and spaced from each other along the axial direction thereof, i.e., direction Z in FIG. 1. Electrically insulating materials 5 are radially disposed in the central support stay 1 along the axis thereof to interrupt undesirable electric current in the circumferential direction of the central support stay 1 as described later.
In the nuclear fusion apparatus described above, an electric current is made to flow through the toroidal coils 2 to confine plasma 4 within the bounds of the coils 2 and an electric current is also made to flow through the poloidal coils 3 to stabilize the position of the plasma 4. At this time, in the toroidal coils 2, an electromagnetic force caused by their respective electric currents is generated as a centripetal force in a radial direction, i.e., direction R in FIG. 1. In the central support stay 1, a voltage in the circumferential direction i.e., direction .theta. is generated by the electric current flowing through the poloidal coils 3.
Accordingly, it is necessary for the central support stay 1 to withstand the centripetal force of the toroidal coils and it is necessary to interrupt the undesirable electric current through the central support stay 1 in the circumferential direction thereof. In the conventional apparatus, the central support stay 1 has a cylindrical shape to withstand the centripetal force and is divided into a plurality of segments in the circumferential direction thereof, with the electrically insulating materials 5 disposed between the segmented portions to interrupt undesirable electric current in the circumferential direction.
In the conventional nuclear fusion apparatus mentioned above, it is difficult to design a central support stay 1 as a structure being circumferentially divided yet still highly rigid in the radial direction. Furthermore, in the conventional apparatus, in order to supply the electric current to the poloidal coils 3, it is necessary to dispose holes on the side surface of the central support stay 1 for passing lead wires therethrough and to carry out brazing etc. in the assembly of the central support stay 1.
Furthermore, in the conventional nuclear fusion apparatus, it is not easy to dispose the poloidal coils in predetermined positions.
To overcome the problems mentioned above, an object of the present invention is to provide a nuclear fusion apparatus in which a central support stay can sufficiently withstand the centripetal force of the toroidal coils and has a high electrical resistance in the circumferential direction of the central support stay, in which the structure of the central support stay is simple and yet facilitates operations for disposing lead wires in the central support stay, etc.
Another object of the present invention is to provide a nuclear fusion apparatus in which the poloidal coils are easily positioned in the circumferential direction of the central support stay.
Accordingly, the present invention provides a nuclear fusion apparatus comprising a central support stay assembly, two or more poloidal coils disposed in the circumferential direction of the central support stay assembly, and two or more toroidal coils radially disposed around and adjacent to the central support stay assembly. The central support stay assembly includes a central support stay portion and a radial arrangement for supporting the poloidal coils and for withstanding the centripetal force of the toroidal coils. The radial arrangement includes two or more radial portions extending radially from the central support stay portion and spaced circumferentially from each other at predetermined angles. Each of the radial portions has a radial member radially extending from the central support stay portion and a force transmission member disposed at the radial outer end of the radial member for transmitting forces from at least two toroidal coils to each radial member.
The invention also provides a nuclear fusion apparatus comprising a central support stay assembly having a central support stay portion and two or more radial portions. The radial portions extend radially from the central support stay portion and are circumferentially spaced from each other at predetermined angles. Each of the radial portions includes a movable radial member which is connected to the central support stay portion and is movable in the radial direction of the central support stay assembly. The nuclear fusion apparatus also comprises two or more poloidal coils which are disposed in the circumferential direction of the central support stay assembly and which are supported by the radial portions. A groove for receiving at least one of the poloidal coils is formed at the radial outer end of each radial member. The nuclear fusion apparatus further comprises a plurality of toroidal coils which are radially disposed around the central support stay assembly and which are adjacent to the radial outer ends of the radial portions.
The present invention further provides a nuclear fusion apparatus comprising a central support stay assembly having a central support stay portion and two or more of radial portions. The radial portions extend radially from the central support stay portion and are circumferentially spaced from each other at predetermined angles. The central support stay assembly is divided into two or more of support stay members in the axial direction of the central support stay assembly. Consequently, the central support stay portion and each radial portion are respectively divided into central support stay segments and radial segments. Each of the support stay members has a hole extending therethrough and the central support stay assembly further includes a bolt inserted into the hole of each of the support stay members and a nut screwed onto the bolt. The nuclear fusion apparatus also comprises two or more poloidal coils which are disposed in the circumferential direction of the central support stay assembly and are supported by the radial portions. Each of the radial segments includes an outer end surface and a step portion for receiving at least one of the poloidal coils. The step portion has a flat portion which is perpendicular to the axis of each support stay member and which is adjacent to the radial outer end surface. The nuclear fusion apparatus further comprises two or more toroidal coils which are radially disposed around the central support stay assembly and which are adjacent to the radial outer ends of the radial portions. Each of the radial segments further includes a portion for withstanding the centripetal force from each of the toroidal coils at the radial outer end of the radial segment.